If boiling water for your French Press is your first action upon getting out of bed, you may want to rethink your morning routine. As a stimulant, we all know the effects that caffeine has, and while many want the benefits of coffee in the morning, it actually may not be the time of day that the caffeine is most effective. In fact, we’ve all had the feeling of “I’ve had two cups and they’re not doing anything!” Why? It has to do with chronopharmacology, the study of how drugs (yes, caffeine is a drug) interacts with your biology.

According to Steven Miller at NeuroscienceDC, one of the most important biological rhythms is your circadian clock, basically the thing in your body that makes you function on a 24-hour cycle. As it turns out, that biological clock actually can alter the effect of drugs, including caffeine.

The main contender when it comes to how caffeine takes affect in your body is cortisol, a hormone related to stress and alertness and, because of the biological clock, whose peak production is around 8 to 9am. In other words, if you are drinking coffee at around the same hour, you are fueling your body with caffeine when your body is already naturally producing what it needs to be alert and you won’t feel the extra effects.

As Miller puts it when you are drinking coffee in the morning, “…you are drinking caffeine at a time when you are already approaching your maximal level of alertness naturally. One of the key principles of pharmacology is use a drug when it is needed (although I’m sure some scientists might argue that caffeine is always needed). Otherwise, we can develop tolerance to a drug administered at the same dose. In other words, the same cup of morning coffee will become less effective…”

So, when is the optimal time to get the benefits of coffee? If you want to drink coffee in the morning, Miller recommends doing it a little later, between 9:30 to 11:30am when your cortisol levels are dropping and therefore you could use a drug induced kick of alertness. In other words, skip the early morning coffee and take a mid-morning coffee break instead.

Completely unrelated to biology, the National Health Service in the United Kingdom determined that the best time to drink coffee is at 2:16 pm, based upon a survey gauging when workers were the most tired. But in regards to the body’s production of cortisol, that makes sense, as other peak times of the day when your body is naturally alert are between noon to 1pm and 5:30 to 6:30pm.

The takeaway? Plan your coffee breaks for mid-morning or mid-afternoon.